REPORT OF THE CHIEF ASTRONOMER 261 



SESSIONAL PAPER No. 25a 



exposed in a high cliff occurs at a meadow on the divide between Priest river 

 and a small fork of Summit creek. Fifty feet to the eastward of this vein are 

 two narrow sill-like injections of minette. This association of vein and erup- 

 tive prompted the assay of the quartz for values in the precious metals. The 

 result was negative. 



The dolomites of the belt characteristically bear isolated crystals and small 

 pockets of . galena and chalcopyrite, and some active prospecting of these rocks 

 has taken place at the forks of Priest river. The sulphides are reported to carry 

 both silver and gold, but so far no workable lode has been discovered. The 

 pockets of galena form the principal 'ore' of the prospect-dumps but the small 

 size and rarity of the pockets — clumps of crystals only a few inches in diameter 

 at most — have led to the abandonment of the claims, which certainly seem to 

 have no commercial value. 



The intrusive rocks occurring in belt A will be described in the section 

 on the igneous bodies of the Selkirks. 



Petrography of Belt B. — The next belt to the east is, so far as lithological 

 types are concerned, very similar to belt A; the chief contrast between the two 

 lies in the different proportions of these types in the belts. Belt B bears thick 

 and persistent bands of dolomite alternating with quartzites and phyllitic and 

 coarser mica schists. The best exposures were seen on the divide between 

 Priest river and Summit creek, to the northwestward of North Star mountain. 

 A tolerably complete section of the belt was there made. 



At the northwest end of this section the western limit of belt B occurs at 

 a bed of silicious dolomite, one hundred feet in thickness. This dolomite is 

 white to bluish white on the fresh fracture but weathers buff-yellow. Though 

 generally massive, it is greatly cracked and shattered, the cracks being filled 

 with vein-quartz which ramifies in all directions through the rock. The strike 

 is N. 9° E.; the dip is practically vertical. 



That limestone is followed on the east by 110 feet of biotite schist, which 

 in turn is succeeded by about 300 feet of thinly laminated, schistose silicious 

 dolomite of colour and composition like the first limestone. This rock too is 

 highly charged with narrow, irregular veinlets of white quartz. The strike is 

 here north and south; the dip, about 65° E. This second limestone is succeeded 

 on the southeast by a 150-foot band of dark, glossy biotite-sericite schist with 

 its planes of schistosity striking north and south and dipping 70° E. It is 

 followed by 95 feet of white dolomitic quartzite (weathering yellowish) with 

 conformable attitude. The quartzite is succeeded by a thick band of light to 

 dark greenish gray phyllitic mica schist. The observed width of this band was 

 1,400 feet across the strike, which runs N. 10° E, The clip is 85° E. On its 

 eastern limit this schist is in contact with a band of dolomitic quartzite of 

 which the thickness measured 340 feet. Here too this rock type is white on 

 the fresh fracture and weathers buff-yellow. The staple dolomitic quartzite 

 is interlaminated with thin beds of nearly pure dolomite and others of nearly 

 pure white-weathering quartzite. The strike is N. 5° E. ; the dip, 85° E. 

 Next to that band, on the east, comes a conformable band of phyllito, followed 



